2.2.1 Criteria for including studies in the review
Types of disorders
For the purposes of this review, cognitive dysfunction was defined as loss of overall intellectual ability due to stroke, as determined by neuropsychological assessments.
Depression after stroke was characterised by the following: low mood; loss of interest or pleasure in all activities; changes in appetite or weight, sleep and psychomotor activity. Other attributes of depression after stroke include: decreased energy; feelings of worthless or guilt; difficulty thinking, concentrating, and making decisions; and recurrent thoughts of death or suicidal ideation, plans, or attempts (American Psychiatric Association, 2013). The reason behind choosing these inclusion criteria was to exclude other types of mood disorders (e.g., bipolar I and bipolar II disorder).
Types of participants
All studies that were eligible for inclusion specified an adult participant sample (18 years old and over). Participants had to have a clinically verifiable diagnosis of stroke. The World Health Organisation defines ischemic stroke as: “rapidly
developing clinical signs of focal or global disturbance of cerebral function, with symptoms lasting more than 24 hours (unless interrupted by surgery or death), with no apparent nonvascular cause” ( Thomas et al., 2000, pp. 1-2).
70 Types of measures
Studies were eligible for inclusion if they:
a) Used a standardised neuropsychological test, which involves one test or a battery of tests, to obtain specific scores for examining overall cognitive dysfunction. These neuropsychological tests are administered under observation in standard conditions and use normative data whereby performance is compared to reference groups of the same age, sex, race, and education level.
b) Included assessment of depression disorder measures to identify and evaluate depression symptoms. The researcher included the rating scales which may be used to detect depression disorders post stroke. These included: the Beck Depression Inventory; Beck Depression Inventory Fast Screen; Brief Assessment Schedule Depression Cards; Center for Epidemiological Studies Depression Scale; General Health Questionnaire with 30 items (GHQ-30) and General Health Questionnaire with 28 items (GHQ-28); Geriatric Depression Scale; Geriatric Depression Scale 15; Hospital Anxiety and Depression Scale; Montgomery-Asberg Depression Rating Scale; Patient Health Questionnaire 2; Stroke Inpatient Depression Inventory; Symptom Checklist 90; Wakefield Depression Inventory; Yale Question. The following questionnaire, not listed by Lincoln et al. (2012), was also included in this review: Hamilton Rating Scale for Depression. The researcher also included questionnaires used with patients with communication problems. These scales included: Aphasic Depression
71 Rating Scale; Depression Intensity Scale Circles; Signs of Depression Scale; Smiley Faces; Stroke Aphasic Depression Questionnaire 10; Stroke Aphasic Depression Questionnaire Hospital version 21; Stroke Aphasic Depression Questionnaire Hospital version 10; Visual Analog Mood Scales; Visual Analog Mood Scales Sad item, Visual Analog Mood Scales Self-Esteem Scale (Lincoln et al., 2012).
Additionally, this review included studies that used either structured or semi- structured interviews to diagnosis depression disorder after stroke. The type of depression measurement was expanded to include the following: Structured Clinical Interview for the DSM-III; Structured Clinical Interview for the DSM-VI; Present State Examination; and Schedules for Clinical Assessment in Neuropsychiatry. When a depression disorder scale was reported in the study and not listed above, the researcher checked back through the references to clarify whether this scale is used to measure depression.
2.2.2 Search method for identification of studies
Types of studies
Published between January 1980 and December 2013, three types of study were selected: identify cohort, cross-sectional and case-control studies. The rationale for the limiting the search to period from the early 1980's onwards was that the examination of the relationship between post-stroke cognitive dysfunction and depression disorder conducted before then was very rare. Furthermore, extending
72 the searches for 33 years allowed including many studies, in order to increase the accuracy of this systematic review.
The review included only those studies that conducted correlation analysis to examine the relationship between overall cognitive dysfunction and depression disorder after stroke. Moreover, it included studies that sought to identify this correlation using at least one of the applications of the correlational statistical techniques. A final restriction pertained to language: non-English studies were excluded.
Study identification
To identify all relevant published studies conducted between January 1980 and December 2013, the following online databases were searched: Medline (May 1981 – December 2013; Appendix 1), EMBASE (March 1983 – December 2013; Appendix 2), and PsycINFO (January 1982 – December 2013; Appendix 3). The search strategy involved combining a number of terms for stroke. These terms included: stroke/ cerebrovascular accidents/ cerebral ischemia/ brain damage/ ischemia/ cerebrovascular disorders/ haemorrhage/ cerebral haemorrhage/ subarachnoid haemorrhage/ cardiovascular system/ geriatrics/ Alzheimer‟s disease/ embolisms/ thromboses. A range of terms describing cognitive dysfunction were also used, including: cognitive ability/ cognitive impairment/ cognitive processes/ cognitive psychology/ cognitive appraisal/ cognitive rehabilitation/ cognitive neuroscience/ cognitive assessment/ cognition/
73 neuropsychology/ neuropsychological rehabilitation/ neuropsychological assessment/ Mini Mental State Examination/ dementia/ vascular dementia/ semantic dementia/ senile dementia/ Alzheimer‟s disease. Likewise, other key terms were used for describing depression disorder: depression/ major depression/ long-term depression (neuronal)/ depression (emotion)/ psychiatric symptoms/ emotional disturbances/ emotional states/ psychiatric evaluation/ psychological assessment/ Beck Depression Inventory/ Zung Self Rating Depression Scale/ Psychological Screening Inventory. All titles identified in the search were reviewed for consideration. In addition, the reference lists of all retrieved studies, as well as the bibliographic references of existing reviews, were subsequently scrutinised for potentially relevant studies. All citations were assessed for relevance based on the study‟s abstract. Where it was not clear whether a study was eligible, the full article was accessed for further consideration.
Data extraction and analysis
To determine whether all the inclusion criteria were met, the researcher reviewed all of the selected articles. The data were then extracted and tabulated before being analysed. The following data were collected about each study:
Full citation: authors; year of publication; country.
Participant characteristics: types of stroke (ischemic, thromboembolic, intracerebral haemorrhage, subarachnoid haemorrhage, undetermined).
Prevalence of overall cognitive dysfunction and prevalence of depression disorder.
74 Study characteristics: sample size; settings; follow-up period.
Assessments used: neuropsychological tests; depression measures.
Findings: correlations between overall cognitive dysfunction and depression disorder post stroke.
The reviewer also assessed the quality of the studies included in the review by adopting the recommendations of the Centre for Reviews and Dissemination (CRD) for undertaking systematic reviews in healthcare. According to the CRD, quality assessment of any study must consider the appropriateness of the study design, the risk of bias, the choice of outcome measures, statistical issues, the quality of reporting, the quality of the intervention, and generalisability. Additionally, the external validity, internal validity and statistical validity of the studies were assessed for measuring the study‟s quality (Centre for Reviews and Dissemination, 2009). The Critical Appraisal Skills Programme (CASP) Checklist for Cohort Study (2013) (Appendix 5) was used to consider the strengths and weaknesses of evidences. The CASP Checklist for Cohort Study includes 12 questions to help in the process of carefully and systematically examining study to judge its trustworthiness, relevance and to assess the quality and validity of the material in each research.